Depends entirely on what part of Europe and which time period you're talking about. Much of Italy, particularly the northern part, was heavily urbanized and the local knights really just provided a mobile striking arm to complement the solid shieldwalls of the communal infantry; ditto for the Low Countries; in the Iberian peninsula lighter cavalry played a greater part due to the geography and the hit-and-run characteristic of many conflicts fought, and the difficult terrain probably kept infantry comparatively valuable too; Fennoscandia was absolutely rotten with dense forests and never good "cavalry country" anyway, as well as so poor proper feudal chivalry were comparatively few in number for economic reasons. France and England, as well as some areas of Central Europe, were relatively open country and prosperous enough to support extensive feudal structures, and it was really there the knights dominated. Germany (as a geographical region) I know less about, but would suspect the trend varied considerably by the specific circumstances and terrain of a given area.
Obviously once you get to the wide open steppes of Eastern Europe and southern Russia, the natural domain of the horse, cavalry becomes rather overwhelmingly dominant for the obvious reason its mobility can be exploited to the fullest; access to traditions of mounted archery and composite bows no doubt further helped in this.
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